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46                          TEETH  AND CLASSIFICATION                       CHAP.
maxilla. There are no vomeiine, palatine, or pterygoid teeth,
such as are met with in Amphibia and E-cptilia.
The other peculiarities of the mammalian teeth, though true
of the great majority of cases, are none of them absolutely
universal.
But it is necessary to go into the subject at some length on
account of the great importance which has been laid upon the
teeth in deciding questions of relationship ; moreover, largely no
doubt on account of their hardness and imperishability, our
knowledge of certain extinct forms of Mammalia is entirely based
upon a few scattered teeth ; while of some others, notably of
the Triassic and Jurassic genera, there is not a great deal of
evidence except that which is furnished by the teeth. Indeed
the important place which odotitography holds in comparative
anatomy is from many points of view to be regretted, though
inevitable. " In hardly any other system of organs of verte-
brated animals/' remarks Dr. Leche, " is there, so much danger of
confounding the results of convergence of development with true
homologies, for scarcely any other set of organs is less con-
servative and more completely subservient to the lightest
impulse from without." Affinities as indicated by the teeth are
sometimes in direct contradiction to those afforded by other
organs; or, as in the case of the simple Toothed "Whales, no
evidence of any kind is forthcoming. Dr. Leche has pointed out
that, judged merely from its teeth, A.retict-is would be referred to
the Itaceoons, though it is really a Viverrid ; while JBas&wise'us,
which Sir "W. Flower showed to be a Haccoon, is in its teeth a
"Viverrid. Mr. Bateson has been obliged to hamper the subject
with another difficulty.
In dealing with the variations of teeth,1 Mr. Bateson has
brought together an immense number of facts, which tend to
prove that the variability of these structures is much greater than
had been previously recognised; that this variability is often
symmetrical; arid that in some animals, as in " Oanis cancrivoru$r
a South American fox, the majority showed some abnormality,"
When we learn from Mr. Bateson that " of Jfylis fontanieri, an
aberrant leopard, two skulls only are known, "both showing dental
abnormalities/' it seems dangerous to rear too lofty a super-
structure upon a single fossil jaw. It must be noted too that,
* Materials for the Study of Variation, London, 1894*